Emulsion aggregation (EA) is a method for preparing toners. EA techniques involve forming an emulsion latex of resin particles by heating the resin using a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Other examples of emulsion/aggregation/coalescing methods for preparing toners are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210, 5,994,020, and U.S. Patent Application Publication No. 2008/0107989, the disclosures of each of which are hereby incorporated by reference in their entirety.
EA toners are sometimes used in forming print and/or xerographic images. Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Patent Application Publication No. 2008/0153027, the disclosure of which is hereby incorporated by reference in its entirety. Incorporating these polyesters into the toner generally requires that the polyesters first be formulated into latex emulsions prepared by solvent containing batch methods, for example solvent flash emulsification and/or solvent-based phase inversion emulsification (PIE).
Oils or waxes are sometimes used to aid in toner release during fusing, and to prevent the fused image document from curling around the fuser roll. However, using oils in a fusing system may cause differential gloss due to oil remaining on the surface of fused prints. A low-oil, or oil-less, fuser system may alleviate issues such as caused by toner-fuser oil interactions, oil contamination, and the like.
A wax may be necessary for a low-oil fuser to function. Waxes aid in preventing document offset, which may occur where fused images become transferred from one document to another (toner-to-toner and toner-to-paper) over a prolonged period of time or at elevated temperatures. In addition, waxes may be added to toner formulations to reduce stripper finger marks, such as scratch marks and changes in image gloss, on the fused images.
Wax is typically added up front with pigment and polyester latex in EA toner methods as a separate, aqueous emulsion. The wax emulsion mixes and aggregates throughout the toner particle formation step. When added as a separate entity during aggregation and coalescence of toner particles, the wax may be rejected by the emulsion or may be incompatible with other toner components. In addition, adding a wax as a separate entity may result in uneven distribution of wax domains throughout toner particles and high wax content on particle surface.
Adding a wax as part of the polyester resin may avoid the separate emulsification step of the bio-based oil and, thus, may reduce the cost of EA toner.
U.S. Patent Application Publication No. 2011/0129774, now abandoned, discloses incorporating an oil component directly into the polyester during the phase inversion emulsification (PIE) stage. However, the oil component in that application was not bonded chemically to the resin, and no covalent bonds were formed. Instead, the oil component was physically trapped inside the core of the latex aggregates. Thus, the oil may flow out of the core making it difficult to control the domains of the wax, or control how the wax is dispersed throughout the toner. Accordingly, a need exists for a method of chemically incorporating a wax into the main chain of a polyester.